Android developers (and apps) already know, if they want to run in the backgroud, they need to implement a service thread. Multitasking works fine where it is needed.

If when porting desktop applications to Android (or to Tizen, JollaMeego), and if it would support for example Qt/C++, multitasking, the OS could by default forbid running on the background. There could be a special dbus-command to system dbus, which would enable application to run also in a background. Also there could be then development option to allow all permissive background processing for all non-android apps.

If a developer porting a desktop application would support that dbus-command, (s)he should follow some guidelines which are good to have if an app is running on a mobile device in a background. Lazy developers would not use this dbus-trick especially when porting, but yet it then wouldn't mind the normal user which do not allow all permissive background processing.